Electric hammer



Dec. 24, '1940.

s. BERMAN 4ELECTRIC HAMMER Filed May 5, 1938 2 Sheets-Sheet 1 729 www@ www INVENTOR.

Dee. 24, 1940. s, BERMAN' 2,225,967

ELECTRIC HAMMER Filed May 5, 1938 2. Sheets-Sheet 2 www ATTORNEY.

- Patented Dee. 24, i940 UNiTED STA-TES PATIENT OFFICE A morale mima Samuel Berman, Bayonne. N. J., assignmto Hammer Standard Electric Co.. Jersey Gity N. J5., a corporation of New Jersey Application May 5, 1938,8erial No. 206,112 2 calma (ci. rizirai This invention relates to electromagnetic devices such as electric hammers. A

One object of the invention is to provide a de-` vice cf the character described wherein a solenoid 5 is provided with improvedv magnetic shielding means whereby the heavy and bulkyplate iamlv nae are eliminated, and the generation of heat.

avoided; and a supplemental object is to furnish an improved method for accomplishing this result.

of an improved electric hammer having improved means to secure the end heads without the loosening action which has heretofore occurred due l5 to the powerful vibration ci' the hammer.

Another object of the invention is to provide an electric hammer having improved means for securing the solenoid and/or the casing end heads, and to prevent undesired turning, lateral or other movement of the solenoid.

;Anotherl object of the invention is to construct an electric hammer having improved 'means to prevent the tool from accidentally dropping out,

. `while permitting free power reciprocation of the 'tool without strain yof said means. A further object of the invention is 'the provision of a device of'the nature set forth having few and simple parts, and which are inexpensive to manufacture and assemble. `and the device being small, compact, light in weight, and durable, re-

liable and eillcient in use. f

Other objects and advantages of the invention will become apparent as the specification proceeds.

' 35 with the aforesaid objects in view, the invention consists in the novel combinations and arrangements of parts hereinafter described in their preferred embodiments, pointed out in the subjoined claims. and illustrated in the annexed 40 drawings, wherein like parts'are designated byy characters throughout the the same reference several views.V In the drawings: A Figure l is a view in longitudinal section showing ,a device embodying the invention.

Fig; 2 is a view of an end plate.

sie s is a top pien view of the solenoid shield-- ing means. Fig. 4 is a schematic elevational view thereof with parts of the solenoid and plunger passage removed and with certain parts of the latter in section.

Fig. 5 is a sectional view on a reduced scale of a modied device embodying the invention, with Another object oi.' the invention is the provision I l ble coil spring 22. The outer end portions of the plungers project through suitable central holes in a part of the solenoid and'its shielding means in elevation.

Fig. 8 is a fragmentary plan view showing an improved means for mounting the wire elements.

Fig.' 'i is a view in elevation showing a modified `il embodiment ofthe principle ofthe wire elements, with a part in section.

Fig. l8 is a top plan view of one part of the same.

section o f the saine.A

The advantages of the invention as here outlined are best realized 4when all of its features and instrumentalities are combined in one and Fig. 9 is a view in side elevation showing one l0 the same structure. but, useful devices may be 16 produced embodyingV less than the whole. f

' It will be obvious to those skilled in the art to which the invention appertaina that the same may. be incorporated `in several different constructions. The accompanying drawing, there- 20 fore, is submitted merely as showing the preferred l threads i3 are the end plates il which are diswithin the casing and-may be considered sto be a part thereof.

Disposed within the casing between the plates il, il is a solenoid means particularly described. Within the solenoid is a Suitable metallic'tubular member I8 that ail'ords a passage for a plurality of reciprocable plungers 0 I2, 20. The latter have their inner ends under- 4 cut as at 2i to form stop portions that are adapt ed to abut each otheron retraction of the plungers. Extending around the stop portions and acting between the plungers I 9, 20 is an expandithe plates Il, I8.

Associated with the casing are the end heads 23, 24, the formerhaving a handle 25 and the 50 latter a nozzle 26v for engaging any'suitable tool 21. Formed on the head 221s a disc portionor wall 28. which may be considered anend wall of the casing, and may have an adjustable central screw means 29 alined with the plunger i9. The 55 I1 hereinafter more I between an expandible coil spring 30.

Formed on the companion plunger 2| is a cylindricalhead 3| which lies in snug fitting relation in a compartment 32 on the head 24. The plate I6 may have an annular lip 33 tightly fitted in the upper end of said compartment .and constituting a stopfor the head 3| to cause a kick back for rapid projection of the power plunger 20. It will be noted that the operation of the stop head 3| and of the plungers and their springs 22 and 38 is in principle the same as described in my patent above mentioned. A cushioning gasket 32a of soft metal, leather or the like may be provided in the chamber 82 for the head 3|.

Heretofore the end heads have been directly threadedly connected to the casing II, but this arrangement has caused excessive strain on the threads and consequent loosening of the heads due to the powerful vibration of the hammer. According to the present invention, the plates I5, I8 are directly threaded to the tubular casing and seat snug against the shoulders I4 thereof. The heads 23, 24 merely have abutment with the ends of the casing Il, as at 34, and are free of the threads I3. To secure the heads to said casing, the screws 35, 36 are utilized, the former passing through the wall 28 and being threaded into the plate I5, while the latter pass through the heavy shock absorbing head 34 and are threaded into the plate I8.

Difficulty had been heretofore encountered in that the solenoid tended to turn and move laterally, axially or both. According to this invention, the screws 35, 38 pass through their respective plates I5, I8 and clampingly or otherwise engage the end rings or non magnetic walls 31 of the solenoid means I1. Preferably the members 31 are formed with recesses 38 and the screws 35, 38 have undercut end portions 38 that snugly fit in said recesses to prevent turning and lateral movement of the solenoid means and to endwise securely support the same at a plurality of points. If desired, the parts 38 of the screws may have. wedging engagement in the recesses for a yielding or adjustable end engagement.

Thus it is perceived that the same means which is utilized to secure the end heads 23, 24 to the casing in an improved manner also reliably xes the solenoid means in position.

Desirably a small clearance space may be provided between the plates I5, I8 and the solenoid end walls I5 as shown. If necessary, the plate I6 may havean annular lip 33a to seat on its shoulder I4. A set screw 34a may lock the head 24 to the casing to prevent turning of the hea and straining of the screws 38.

' A dimculty had been encountered in that the tool frequently fell from the Ahammer when lifted'from the work. Accordinrto the present in-A vention, the shank 4,0 of the tool 21 is received in a vguide passage 4I of the nozzle 28. which also receives a projecting impact portion 42 of the power plunger 2l, but the shank 40 is formed Lwith' a longitudinal, preferably annular groove 43 in which there may engage a removable set screw 44. 'I'he length of the recess 43 is preferably such as to afford ample clearance for reciprocation without impact on the set screw, whereby excessive strain on the latter is'avoided.

Frequently it has been found that dus't would settle in the path of the power plungers of`electric hammers and seriously interfere with their latter and the screw'means may mount there-I operation. According to the present invention, the parts I8, 24, 3l and 42 interflt so snugly that practically no dust can enter. In other words, the power plunger forms a plug-like closure, whereas heretofore hammers of this type generally afforded central passages through which dust could readily enter the plunger passages.

The solenoid means I1 will now be described. The same includes any suitable winding 45 and is preferably operative by both D. C. and A'. C.

currents. When the solenoid is Worked by A. C. current, considerable heat is generated, the dissipation of which cannot be effectively accomplished by ventilation, and has heretofore presented a problem. In commercial electromagnetic hammers, it is customary to use plate laminae surrounding the solenoid, but Ithese greatly add to the weight and bulk of the hammer and constitute a drawback in a portable device. For instance, such laminations increase the diameter of the hammer by approximately one-third. The present invention aims to overcome this diillculty and, in a certain sense, may be considered to be of general application in the electrical art and as involving a new method for electromagnetic shielding. A

Briefly described, the solenoid I1 includes shielding means 46 which consists of Wire-like elements arranged about the solenoid or along a surface portion thereof in a laminated-like manner. 'I'hese wire-like elements are set together as closely as possible and are insulated from each other by shellac, Bakelite or other suitable insulation. In cross section. said elements may be of any suitable shape or size, for instance, as small as nl! inch and as large as 1/2; inch in diameter. The wire shape is desirable because it is very inexpensive to produce, but it tends to limit the diameter to the smaller sizes. To concentrate the electromagnetic force at a point Where it will be most effective, namely, at the central inner region of the solenoid adjacent to the inner ends ofione or both of the plungers I9, 20, the shielding means extends along the solenoid passage except at the said central region. In such a case, it is desirable to inv terrupt the wire-like elements at points outside of said passage. The sleeve I8 is of course nonmagnetic so as to permit normal operation of the plungers by the induction coil. But the plates 31 vare deslrably of magnetic material to afford a substantial eld for magnetic flux. This fieldv at each plate 31 should have an area equal to its thickness multiplied by the circumference of the plunger hole in the plate. The magnetic shieldlng elements 41, 48 hereinafter described may be insulated from the plates 31 as by enamel coating.

Specifically, the shielding means 46 may include the straight elements 41 secured parallel to the solenoid axis along the outer surface of the winding 45, and may also include. the L-shape wire elements 48 at the op-posite ends of the solenoid. The elements 48 have their longer arms 49 lying along the solenoid passage, and their shorter arms 58 lying radially along the ends of the solenoid winding. The elements 41 and 48 are interrupted at 5I, being insulated from each other at this point. Ifdesired, the elements 41, 48. may lie in like radial planes, but this is unnecessary.

As shown in the drawing, the arms 49 lie between the metallic guide sleeve I8 and the insulator sleeve or core 82 of the solenoid.

In operation, the shielding means 46 eliminates magnetic eddy currents, and other losses, and hence prevents overheating. Alsothe magnetic ends of the arms 49, and additional shielding is obtained in this manner. These features have been thoroughly tested on an electric hammer that was subjected to a long period of actual industrial use.

In Fig. 5 is shown a modified device 5I embodying the inventiomand which is generally like the device I0, except as otherwise stated. Principally, it is noted that one plunger 541s fixed, being threadedly connected to the'plate lia or the head 23a or bo'th, as shown, to thus provide a rigid core acting as a kick back" abutment for the power plunger 20a. The head Ila voi' the latter mayv have an annular shoulder 54, an expansion coil spring 55 acting between the latter and the plate IB toproject the power plunger after retraction thereof by the solenoid. By locating the spring outside of the solenoid, a large spring of ample power and life may be used.

In operation', the solenoid retracts the plunger 20a so that it strikes the fixed core 54 causing a reaction which sends the power plunger forward to supplement the action of the spring 55.

the plate. Disposed beyond the closed ends of the slots II and in radial alinement therewith are openings or holes 59 which may be in the nature of openr ended slots, of slightly keyhole form, shown somewhat exaggerated in the drawings. It will now be perceived that the slots |58 snugly receive along the plane thereof the arms 54 of the. wire elements 48, and the ends of the wire elements 41 may be engaged in the openings 58 as by being pressed orsprung thereinto laterally or axially. The plates I1 will serve to maintain the members 41, 48 and i1 in assembly relation, with thermembers 51, top and bottom, serving to hold the wire elements in place If necessary, the plates l1 may be pinched at the open ends of the slots 5I to securely grip the wire elements 41. ILdes'ired, a suitable shelf hardening 'adhesive coating of shellac or the like may additionally interconnect the part's 41, 48 and 51 to facilitate assembling. The-means IQ will securely hold the wire elements dislodgement by vibration.

By making the-fplatel1 relatively thick, that is, thicker than the.. wire element. 48, the latter andthe wire elements 41 can be maintained out trating a modified form ofthewire elements 41,

4l to facilitateassembling-of the device il. `The same in ygeneral illustrates a sheet metal structure providing a substantial equivalent of the wire elements-41, 44. 'Thus the wire elements 41 are replaced by ashellli havingoifig slots Il providing oppositely projecting staggered tongues v or strips 4I. Centrally vdisposed in thesheil ll'are a plurality of'alined'shells I4 whichreplac'e-the arms 4I. The shellsM; like those'shown at ll,

nave 'onset slots il affording onpcsiteisg` proietting staggering tongues 4t;- Inplsce of arms toward the element Bl.

M, a pair of ring plates 61 are provided having radial offset inner and outer slots 88 affording `oppositely extending tongues 88. By using relatively thin sheet metal, preferably less than IAG of an inch in thickness, the cross sectional area of the different tongues may be quite small. The elements 4I, i4 and 01 may be interconnected in any suitable manner, by screws, rivets or by welding.. For example, the plates 61 may have outward extending tongues 10 arranged to mate with laterally bent tongues 'lll of the shell 80 at the free edges'of the latter, andl these parts 10, 1i being spot welded together. To afford a magnetic spacing between the elements 6l, 61, the tongues 10 may be bent from the plane of the plates 61 Likewise the elements I4 may have marginal tongues 12 outwardly but also axially bent to contact the elements 81 for spot welding thereto. It will be appreciated that the shells il, 64 may be struck in the form of plane sheets, and then bent into the cylindrical form as indicated by the split at Sla. Further, it will be perceived that the plates 61, like the arms 50,

may be coated at their opposite faces with a suitable material or filler 13, such as shellac, to afford a magnetic spacing from the plates 31 and between the elements 6|, 01, especially as the plates 81 are subject to the pressure of the plates 31. If preferred, the coil may itself afford a support for the plates 61 to prevent the same from being pressedv into contact with the shell 6I. The projections at 10, 1I may form' a spacing means with the casing I I, or other spacing means may be used. 4 y

Preferably the plates 61 and B1 consist of magscribed for the plates '31. In that event, the wire elements 4l .may be insulated therefrom, as by enamel coating, if desired, although such insulation may be dispensed with.

It 4will be understoodthatthe structures of Figs. 6 to 8 may 'also be used with the device of Fig. 5 as well as with that of Fig. 1.

If preferred, the plates such as 31, 51 and l1 may consist of laminae; and, further, the wire portions 49 may be replaced by a coaxial series of wire rings or laminae. But the preferred constructions are those herein shown.

I claim:

l. A device including an electric hammer comprising an open ended casing, a solenoid therein removably engaged to said plates and having abut-V ment with the ends of the cylinder, and means connecting said heads to said plates including screw elements having inward projecting ends,

netic material and are of sufficient thickness` to* anord an ample ileld for magnetic ux as deand the solenoid having means having recesses receiving the projecting screw ends so as to secure the solenoid in position. ,i

'2. A device including an electric hammer., comprisinga solenoid for actuating a power plunger and magnetic shielding means therefor, comprising a plurality of spaced wire-like elements along theoutside of the solenoid, a plurality of spaced I angle wire-like elements each having an arm extending along the bore of vthe solenoid and a second arm extending-generally radially along an endo( the solenoid, and securing me vfor saideleinents` comprising end plates of'nonmagnetic material having ope l to receive and engage the end portions of said-c ements,

I vsluunin.'maximum. 1s n 

